The present invention relates to a long life composite member such as a long life composite fuser roll and a long life composite pressure roll that are especially useful in a fusing system in an electrophotographic reproducing apparatus including digital and color apparatuses and processes. In particular, the present invention relates to a fuser roll and a pressure roll having excellent wear resistance properties.
In a typical electrophotographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
One of the more common approaches to thermal fusing of toner images is by the concurrent application of heat and pressure by various means such as a roll pair including a heated fuser roll and a pressure roll which are maintained in pressure contact through a fusing nip. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time are applied.
It is known to prepare a backup, fuser, or other type roll by utilizing one or more layers on a metal core. For example, U.S. Pat. No. 4,207,059 describes a backup roll constructed of a core member of heat conductive material and a heat insulative coating provided on the surface of the core member in at least the areas where it may make direct contact with the heated fuser roll. For instance, a backup roll is constructed of an aluminum core member coated with polyurethane reinforced fluorinated ethylene propylene.
U.S. Pat. No. 4,254,732 describes a backup or pressure roll having a solid metal core having adhered thereto a relatively thick layer of deformable material such as an elastomer of an ethylene-propylene terpolymer. U.S. Pat. No. 5,547,742 describes a fuser roll having a metal core shaft and a silicone rubber surface layer, such as polytetrafluoroethylene, tetrafluoroethylene/hexafluoropropylene copolymer, tetrafluoroethylene/ethylene copolymer, or tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer. U.S. Pat. No. 3,912,901 describes a roll having a rigid core covered with a relatively thick elastomeric layer with a relatively thinner sleeve or layer of a high flex life material forming an outer surface for the roll. U.S. Pat. Nos. 5,709,949 and 5,547,759 describe a method of making a fuser member such as a fuser roller, pressure roller, or fuser belt, comprising bonding an outermost fluoropolymer resin layer to an inner fluoroelastomer layer by means of a fluoropolymer-containing polyamide-imide primer layer.
U.S. Pat. No. 5,291,257 describes a pressure roll that has a core and a surface coating that has been heat cured from a composition of a fluorocarbon polymer and an irregularly shaped, nonplanar, inert filler having a hardness greater than 8 Mohs. The filler has a nominal particle size of from about 10 to 30 microns and is present in the cured surface coating in an amount of from about 10% to 40% by weight of the total solids weight of the coating.
It is important that the pressure roll and fuser roll be durable and long-lasting. Otherwise, the rolls would require frequent replacement which is expensive and time consuming. Thus, the pressure roll and the fuser roll should each have a coating (top layer) that is very durable and long lasting. Typically, such properties are imparted by a top layer containing a powder mixture of silicon carbide (SiC) and perfluoroalkoxy (PFA) TEFLON. However, there have been difficulties associated with providing a suitable coating with this powder mixture.
First, because of the electrostatic differences between silicon SiC and PFA, it is difficult to provide a uniform distribution of SiC to the surface of the roll during electrostatic application. The PFA adheres uniformly to the roll but the SiC does not. As a result, insufficient SiC is applied to the roll and the SiC content on the roll is not uniform.
Second, because the SiC and PFA are applied as a powder, there is a lot of wasted powder which falls to the bottom of the application equipment as over spray. Further, because of the electrostatic differences between silicon SiC and PFA discussed above, SiC does not sufficiently adhere to the roll but instead drops to the bottom of the application equipment along with the wasted powder. It is difficult to predict and control how much of the SiC adheres to the roll and how much falls to the bottom. Since over sprayed powder collected at the bottom is a mixture of over sprayed PFA and SiC powder together with SiC powder that did not adhere to the roll, it is likewise difficult to determine the percentage of SiC in the bottom powder mixture.
Testing methods, such as thermogravimetric analysis, do not work well. During the thermal decomposition of TEFLON, HF is formed which subsequently reacts with Si to form volatile SiF4. The volatile SiF4 causes deviations in thermogravimetric analysis such that the results indicate less SiC% than there actually is. Hence, an accurate amount of SiC in the waste powder cannot be readily determined and the waste powder cannot be reused in the present prior art processes.
Thus, it is desirable to provide a composite roll that is durable and long lasting, but does not have the waste associated with the prior powder coating methods.
Accordingly, the present invention is directed to providing a durable, long life, wear resistant composite member such as, but not limited to, a composite fuser roll or a composite pressure roll, prepared from a polymer liquid having a homogenous distribution of ceramic-based particles such as SiC particles.
Composite members containing ceramic-based particles in accordance with the present invention have a prolonged life of, for example, at least 10% over the life of a composite member without ceramic particles.
In one embodiment, the present invention is directed to a composite member comprising a substrate, a first layer, a second layer, and a surface layer, wherein the second layer comprises a polymer having ceramic-based particles substantially homogeneously distributed throughout the polymer and protruding from the surface of the polymer layer into the surface layer. In another embodiment, the present invention is directed to a composite member comprising a substrate, a first layer and a surface layer wherein the first layer comprises a polymer having ceramic-based particles substantially homogeneously distributed throughout the polymer and protruding from the surface of the polymer layer.
In a preferred embodiment, the member is a roll and the substrate is a core, preferably of steel or aluminum.
In a further embodiment, the polymer is a fluorocarbon polymer, more preferably, selected from the group consisting of polytetrafluoroethylene, perfluoroethylene perfluoroalkylvinylether and mixtures thereof.
In a further embodiment, the ceramic-based particles preferably comprise SiC, alumina, or mixtures thereof, most preferably SiC. Preferably, the average size of said ceramic-based particles ranges from about 5 to about 30 microns, more preferably, about 20 microns, and said ceramic-based particles are present in an amount from about 5% to about 40% by weight solids based on total weight of the second layer.
Another embodiment is a fuser system which comprises a fuser roll and a pressure roll provided to form a fusing nip therebetween for fusing a toner image to a substrate, wherein at least one of said fuser roll or said pressure roll comprises a core, a first layer, an optional second layer, and a surface layer wherein at least the first layer or optional second layer comprises a polymer having ceramic-based particles substantially homogeneously distributed throughout the polymer and protruding from the surface of the polymer layer.
In a further embodiment, the polymer is preferably selected from the group consisting of polytetrafluoroethylene, perfluoroethylene perfluoroalkylvinylether, and mixtures thereof. The ceramic-based particles preferably comprise SiC, alumina, or mixtures thereof, preferably SiC. The average size of the ceramic-based particles ranges from about 5 to about 30 microns, preferable about 20 microns, and the particles are present in an amount from about 5% to about 40% by weight solids based on a total weight of the first layer.
A further embodiment is a method of making a composite member comprising forming a polymer layer on a substrate by applying to said substrate a composition comprising a liquid fluorocarbon polymer having a substantially homogenous distribution of ceramic-based particles, drying to form a polymer layer having said particles protruding from the surface of said polymer layer, and then applying a surface layer to said polymer layer. In another embodiment, a first layer is applied to the substrate prior to forming a polymer layer.
Preferably, the average size of said ceramic-based particles ranges from about 5 to about 30 microns and the ceramic-based particles are present in an amount from about 5% to about 40% by weight solids based on total weight of the polymer layer.
In yet enother embodiment, the present invention is directed to an electrophotographic system comprising a fuser component and a pressure component provided to form a fusing nip therebetween for fusing a toner image to a substrate, wherein at least one of said fuser roll or said pressure component comprises a core, a first layer, an optional second layer, and a surface layer wherein at least the first layer or optional second layer comprises a fluorocarbon polymer having ceramic-based particles substantially homogeneously distributed throughout the polymer and protruding from the surface of the polymer layer.